Thumbs, Toes, and Tears

by Chip Walter

  Paleoanthropologists aren’t completely in agreement about when our ancestors began to walk and why. The most accepted theory is that hominids began to walk upright after they were forced to deal with the climatic destruction of many of Africa’s jungles beginning about six million years ago. At that time, most of Africa was forested. But recent fossil discoveries have called that theory into question. In 2001, anthropologists found fragments of skull, hand, arm, and collarbone fragments from a creature (Ardipithecus ramidus kadabba) that lived in the Middle Awash River Valley of Ethiopia almost 5.2 to 5.8 million years ago. Of all the bones they found, though, the most interesting was a single toe bone that indicated this animal could stand upright. What makes this odd is that other fossil studies of the region’s soil indicate that six million years ago this part of Ethiopia was forested. So if it was the spread of savannas and grasslands that forced early hominids to stand on their hind legs, why was this creature walking upright when it was still living in a jungle? Maybe the toe is misleading. It may be that beyond the forest where the creature lived there were wide-open spaces that required upright walking. It may mean that this creature was an evolutionary aberration. Some scientists have speculated that early creatures from this period became “preadapted” for walking upright by walking along the branches of large trees. Whatever the case, somehow creatures ancestral to us eventually stood up, evolved in the open savannas of East Africa, and led to the creatures we are today.

  4. M. Brunet, et al., “A New Hominid from the Upper Miocene of Chad, Central Africa,” Nature 418 (2002): 145–51; P. Vignaud, et al., “Geology and Paleontology of the Upper Miocene Toros-Menalla Hominid Locality, Chad,” Nature 418 (2002): 152–55.

  5. For more information about the Laetoli footprints see

  http://www.asa3.org/archive/evolution/199505-10/0668.html.

  6. From Donald Johanson and James Shreeve, Lucy’s Child: The Discovery of a Human Ancestor (New York: William Morrow, 1989).

  7. Some scientists who have studied Lucy argue that she was a tree-dweller, at least part-time, because she has a bone in her wrist that enabled her to knuckle-walk. The theory is that she would not have retained this bone if she hadn’t preserved some of the ambulatory habits of her precursors. But other scientists argue that having the bone doesn’t mean it was used. It may simply have been an evolutionary leftover, like wisdom teeth or appendices.

  8. For more on this see

  http://www.webster.edu/~woolflm/maryleakey.html.

  9. To read a revealing profile of Mary Leakey visit

  http://www.sciam.com/article.cfm?articleID=0006E1CC-7860-1C76-9B81809EC588EF21&pageNumber=2&catID=4".

  10. Donald C. Johanson and Maitland A. Edey, Lucy: The Beginnings of Humankind (London: Penguin, 1981), p. 250.

  11. For some disagreement on the humanness of the Laetoli footprints read Ian Tattersall and Jeffrey H. Schwartz, Extinct Humans (Boulder, Colo.: Westview Press, 2001).

  12. Compared to modern humans, A. afarensis was small. Males probably stood about four feet, eleven inches high and weighed about a hundred pounds. Females were even smaller, stood about three feet, five inches tall, and weighed about sixty-two pounds.

  13. The fossil record reveals many examples of this from microscopic creatures such as foraminiferans (single-celled protists with shells) to various species of trilobites, even the rapid emergence of a descendant of Tyrannosaurus rex known as Daspletosaurus (frightful lizard), which roamed the plains of Montana and western Canada during the Cretaceous period, about seventy-five million years ago.

  14. Whether it is in insects or human beings, HOX genes are lined up tightly in chromosomes, like pearls on a string. Scientists speculate that this grouping and sequence are necessary for the genes to function in a coordinated way. For example, the HOX gene sitting first in line on the chromosome controls the development of the back part of the brain, the second gene is responsible for the upper part of the neck, and so on along the body axis. If they get out of sequence, the body parts they govern would also be physically expressed out of sequence.

  15. See Jeffrey H. Schwartz, Sudden Origins: Fossils, Genes, and the Emergence of Species (New York: John Wiley & Sons, 1999).

  16. For more information about early forested habitats see

  http://www.sciencedaily.com/releases/2001/07/010712080455.htm

  and Kate Wong, “An Ancestor to Call Our Own,” Scientific American 13(2) (2003), 4–13.

  17. The lack of trees also means that the grasslands were short on shade, another powerful reason for standing upright. In the jungle, shade was abundant, and there was little need for hominids to reduce how much of their dark and hairy body they exposed to the sun. But under the hot savanna sun, standing erect shades more of the body from the broiling heat at the same time it exposes more of it to the air. Both have a chilling, well-cooling effect. More on this in chapter 5, “Making Thoughts out of Thin Air.”

  18. At a speed of two miles an hour, a chimpanzee expends about a third more energy than a human. Over the long haul, that simply wouldn’t do. (See Rodman and McHenry, “Bioenergetics and Origins of Hominid Bipedalism,” American Journal of Physical Anthropology 52 (1980): 103–106.) Later studies supported Rodman and McHenry’s argument for the energy efficiency of human bipedal walking as compared to chimpanzee quadrapedal locomotion.

  19. Scientists have to be careful when drawing conclusions about an animal’s behavior from its anatomy, but the fossil evidence suggests that these robust, big-toothed australopiths relied more on roots and nuts for their nourishment than the gracile apes such as A. africanus, which seem better suited to an occasional meal of carcass scraps and mashed bone marrow. We see something similar to this in the eating habits of gorillas and chimpanzees today. Gorillas are almost exclusively vegetarians, and they have the teeth and jaws to prove it. Chimps, as Jane Goodall’s studies have shown, will eat meat when they can, and even cooperatively hunt down bush pigs and small monkeys. Paranthropus robustus’s vegetarian ways may ultimately have been its undoing, because the line seems to disappear about 1.5 million years ago without, so far, another fossilized peep. The evolutionary advantage apparently fell to apes that could complement their diet of bugs, roots, and berries with animal fat and protein.

  Chapter 2: Standing Up—Sex and the Single Hominid

  1. Charles Darwin, The Descent of Man (Norwalk, Conn.: Heritage Press, 1972), p. 187.

  2. See the following for more on this subject:

  Berscheid Ellen, and Harry T. Reis. “Attraction and Close Relationships.” In Daniel T. Gilbert, Susan T. Fiske, and Gardner Lindzey, eds., Handbook of Social Psychology (New York: McGraw-Hill, 1998), pp. 193–281.

  Harper, B. “Beauty, Statute and the Labour Market: A British Cohort Study.” Oxford Bulletin of Economics and Statistics 62 (December 2000): 773–802.

  Fisher, Helen. “Why We Love: The Nature and Chemistry of Romantic Love.” New York: Henry Holt, 2004.

  Cash, T. F., B. Gillen, and D. S. Burns. “Sexism and ‘Beautyism’ in Personnel Consultant Decision Making.” Journal of Applied Psychology 62 (1997): 301–10.

  Clark, M. S. and J. Mills. “Interpersonal Attraction in Exchange and Communal Relationships.” Journal of Personality and Social Psychology 37 (1979): 12–24.

  Cunningham, M. R. “What Do Women Want?” Journal of Personality and Social Psychology 59(1990): 61–72.

  Singh, D. “Adaptive Significance of Female Physical Attractiveness: Role of Waist-to-Hip Ratio.” Journal of Personality and Social Psychology 65 (1993): 293–307.

  Cunningham, M. R., A. R. Roberts, A. P. Barbee, P. B. Duren, and C. H. Wu. “Their Ideas of Beauty Are, on the Whole, the Same as Ours: Consistency and Variability in the Cross-Cultural Perception of Female Physical Attractiveness.” Journal of Personality and Social Psychology 68 (1995): 261–79.

  De Santis, A., and W. A. Kayson. “Defendants’ Characteristics of Attractiveness, Race, and Sex and Sentencing Decisions.” Psychological Reports 81 (1999): 679�
�83.

  3. Timothy Taylor, The Prehistory of Sex (New York: Bantam Books, 1996).

  4. S. R. Richards, F. E. Chang, B. Bossetti, W. B. Malarkey, and M. H. Kim, “Serum Carotene Levels in Female Long-Distance Runners, Fertil Steril. 43, no. 1 (1985): 79–81; C. H. Wu and G. Mikhail, “Plasma Hormone Profile in an Ovulation.” Fertil Steril. 31, no. 3 (1979): 258–66.

  5. Nikolas, Lloyd, “Why Women Have Breasts” (see

  http://www.staff.ncl.ac.uk/nikolas.lloyd/evolve/breasts.html).

  6. In addition to the work of Rosenberg and Trevathan, C. Owen Lovejoy at Kent State University and Robert G. Tague of Louisiana State University have studied a range of fossil pubic and pelvic bones and concluded that while the birth canals of australopiths are larger than a human’s, the baby still would have had to rotate either forward or backward to fit its shoulders through the narrowing canal. This means that sometimes the baby would have been born facing its mother’s back or facing forward. Either way it would have been more difficult than the average chimpanzee’s birth, and that would have required some help. From Karen Rosenberg and Wenda R. Trevathan, “The Evolution of Human Birth,” Scientific American 13(2) (2003). Also see C. Owen Lovejoy, “The Evolution of Human Walking,” Scientific American (November 1988).

  7. Various versions of Homo habilis fossils have been found, and many are debated. Some date back as far as 2.3 million years ago.

  8. Stephen Jay Gould, Ontogeny and Phylogeny (Cambridge, Mass.: Harvard University Press, Belknap Press, 1997), pp. 372–73.

  9. Ibid., pp. 352–56, and

  http://www.serpentfd.org/a/gouldstephenj1977.html

  for details.

  10. Gould, Ontogeny and Phylogeny, p. 401.

  Chapter 3: Mothers of Invention

  1. For a short movie that illustrates these corpuscles visit

  http://www.microscopyu.com/galleries/confocal/meissnerscorpusclesprimate.html.

  2. Shakespeare had an enormous influence on the vocabulary and expression of the English language. He invented more than seventeen hundred words (not to mention countless phrases that we all commonly use every day). He did this mostly by changing nouns into verbs or verbs into adjectives, or by putting two words together that had never before been connected. Sometimes he added prefixes and suffixes, and often he made new words out of whole cloth. A short list of some words the great bard invented include advertising, amazement, arouse, assassination, backing, bandit, bloodstained, bump, buzzer, circumstantial, cold-blooded, compromise, dauntless, dawn, dishearten, drugged, dwindle, frugal, generous, gloomy, gossip, gust, hobnob, impartial, invulnerable, lackluster, laughable, lonely, luggage, lustrous, madcap, majestic, mimic, monumental, moonbeam, obscene, olympian, outbreak, radiance, rant, remorseless, savagery, scuffle, submerge, summit, swagger, torture, tranquil, undress, unreal, worthless, zany. For more visit:

  http://shakespeare.about.com/library/weekly/aa042400a.htm

  or read Coined by Shakespeare by Jeffrey McQuain and Stanley Mallessone (Springfield, Mass.: Merriam-Webster, 1998).

  3. See In the Shadow of Man by Jane Goodall for more on the tool use of chimpanzees (and everything else about their lifestyle in the wilds of Africa).

  4. John Napier, Hands, rev. ed. (Princeton, N.J.: Princeton University Press, 1993), p. 55.

  5. Mary Marzke, “Evolution,” K. M. B. Bennett and U. Catilello, eds, Insights into the Reach to Grasp Movement (Amsterdam: ElsevierScience B.V., 1994), chapter.

  6. Kathy D. Schick and Nicholas Toth, Making Silent Stones Speak: Human Evolution and the Dawn of Technology (New York: Touchstone Books, 1993).

  7. Beginning with excavations on July 21, 1986, in Olduvai Gorge, important portions of Homo habilis’s body were found and reconstructed (one key assemblage of fossils is known as OH 62).

  Until 1986 Homo habilis had been considered ancestral to modern humans and a direct ancestor of Homo erectus, so its limb proportions were thought to be similar to modern humans. But the OH 62 skeleton revealed that H. habilis had surprisingly apelike limb proportions.

  Modern humans have an upper arm bone (humerus) which is considerably shorter than the upper leg bone (femur). In modern apes the humerus and the femur are nearly the same length. This means that Homo habilis had a body structure much more like an ape or Australopithecus afarensis, than like a modern human. OH 62 also was small—about three feet tall—and probably a female. This implies a significant amount of sexual dimorphism, again, more like apes or A. afarensis than modern humans, where the difference in size between men and women is not so great. Both of these finds were surprising.

  8. “We acquire a large system of primary metaphors automatically and unconsciously simply by functioning in the most ordinary of ways in the everyday world from our earliest years. We have no choice in this. Because of the way neural connections are formed during the period of conflation, we all naturally think using hundreds of primary metaphors.” Philosophy in the Flesh by George Lakoff and Mark Johnson (New York: Perseus, 1998), p. 47.

  9. From the work of Srini Narayanan, one of Lakoff’s students. For more see

  http://www.google.com/search?q=Narayanan+neural+theory&ie=UTF-8&oe=UTF-8.

  10. P. M. Greenfield, “Language, Tools, and Brain: The Ontogeny and Phylogeny of Hierarchically Organized Sequential Behavior,” Behavioral and Brain Sciences 14 (1991), 531–51, and P. M. Greenfield. “Language, Tools, and Brain Revisited,” Behavioral and Brain Sciences (1991): 531–95.

  11. We are unique in this among species partly because the mental lives of all animals are shaped by their physical experience. Dolphins and whales sense their surroundings with elaborate sonar echolocation techniques and communicate by rich suites of clicks. In his book The Dragons of Eden (New York: Ballantine Books, 1977), pp. 107–8, Carl Sagan pointed out, “One very clever recent suggestion, which is being investigated, is that dolphin/dolphin communication involves a re-creation of the sonar reflection characteristics of the objects being described. In this view a dolphin does not ‘say’ a single word for shark, but rather transmits a set of clicks corresponding to the audio reflection spectrum it would obtain on irradiating a shark with sound waves…. The basic form of dolphin/dolphin communication in this view would be a sort of aural onomatopoeia, a drawing of audio frequency pictures—in this case caricatures of a shark. We could well imagine the extension of such a language from concrete to abstract ideas…. It would be possible, then, for dolphins to create extraordinary audio images out of their imaginations rather than their experience.” In this sense, echolocation (the dolphin equivalent of hands and eyes) shapes clicks (the dolphin version of language). Whether they have made that leap isn’t yet fully understood.

  12. Sherman Wilcox, “The Invention and Ritualization of Language” in Barbara J. King, ed., The Origins of Language (Santa Fe, N. Mex.: School of American Research Press, 1999).

  13. M. A. Arbib, “From Monkey-like Action Recognition to Human Language: An Evolutionary Framework for Neurolinguistics,” Behavioral and Brain Sciences (revision completed February 1, 2004), with the author’s response to the commentaries on the article (completed August 22, 2004).

  14. In still another study that Japanese researchers conducted forty-seven functional magnetic resonance imaging (fMRI) that revealed that people adapt when they wear specialized glasses that reversed the images of their right and left hands. When they picked up a ball with their right hand the glasses reversed the image so that it looked as though it was actually their left hand doing the grasping. It took participants in the study nearly a month to straighten out the garbled signals their brains were receiving, but again, it turned out that Broca’s area was behind most of the straightening out, resyncing the signals being sent from the eyes and the hands. This confirmed that Broca’s area is not only central to speech, but also crucial to coordinating how we handle and manipulate objects.

  In another, more recent study, Marco Iacoboni at the Los Angeles School of Medicine found that Broca’s area “lit up” wh
en subjects watched another person trying to accomplish a task. “Cortical Mechanisms of Human Imitation,” Science 286 (1999): 25–26.

  15. Charles Darwin, The Descent of Man, and Selection in Relation to Sex (Norwalk, Conn.: Heritage Press, 1972).

  16. “Meme” is a word coined by Oxford zoologist Richard Dawkins, who has argued that like genes, which are preserved in species because they lead to traits that enable survival, memes are ideas or concepts that survive, flourish, and are adopted in cultures because they work. Riding horses is a meme that was adopted by cultures around the world as a terrifically efficient way to get around. Agriculture is a universally adopted meme, except for those few hunter-gather tribes that persist in remote parts of the world. Watching movies on DVDs or communicating by e-mail also are memes that are flourishing, just as the genes that enabled upright walking, speech, and music are regularly returned and then drawn from the same gene pool.

  Chapter 4: Homo hallucinator—the Dream Animal

  1. For more on the origins of language see Eric P. Hamp and E. H. Sturtevant, Linguistic Change: An Introduction to the Historical Study of Language (Chicago: University of Chicago Press, 1961).

  2. From Derek Bickerton, University of Hawaii, in his book Roots of Language (Ann Arbor, Mich.: Karoma Publishers, 1981).

  3. For a broad and fascinating (but sporadic) survey of nonverbal forms of communication and the science behind them, visit the Web site of the Center for Nonverbal Communication at

  http://members.aol.com/nonverbal2.

  4. Some scientists believe that vocal language may date back only about two hundred thousand years. Even as human primates, we have not fully come to grips with the prolonged, face-to-face closeness required for speech. Speaking to a stranger, for example, stresses our autonomic nervous system’s sympathetic (fight-or-flight) system. That then speeds our heartbeat, dilates our pupils, and cools and moistens our hands. The limbic brain’s hypothalamus also instructs the pituitary gland to release hormones into the circulatory system, increasing the flow of our blood, sweat, and fears.